A famous radio talk show host asked rhetorically why unions have supported and financed the Occupy Wall Street movement. The answer is quite simple. Occupiers are asking for communism. In communism, the entire labor force is unionized. It is in the best interest of unions to promote communism since union membership in this country is down to single digits and not likely to rebound.
Unions were necessary at the turn of the 20th century to protect workers from dangerous working conditions. Unions survive today as a political tool to influence elections and exert economic power.